FIG. 12 is a block diagram schematically showing a conventional type of charging apparatus disclosed, for instance, in Japanese Patent Laid-Open Publication No. HEI 5-38058. The charging apparatus shown in FIG. 12 comprises an AC circuit unit 102 and a DC circuit unit 105 with a connector 109 provided therein, and connects the AC circuit unit 102 to the connector 109 of the DC circuit unit 105 for electrical connection between the circuit units.
The AC circuit unit 102 comprises an AC adaptor circuit 103 for converting an AC power supplied from an AC input receptacle 101 to a DC power, and a charging circuit 104 for controlling a charging operation of the DC circuit unit 105.
The DC circuit unit 105 comprises the connector 109 for electrical connection to the AC circuit unit 102, a battery pack 108 which is a secondary battery to be charged, switches SW1 and SW2 each for controlling charging and power supply, a DC--DC converter 106 for converting a DC power supplied from the battery pack 108 or an AC adaptor circuit of the AC circuit unit 102 to a required working voltage, and a logic circuit 107 for receiving a DC power and driving the DC circuit unit 105.
Next description is made for operations. In the charging apparatus shown in FIG. 12, when the AC circuit unit 102 and the DC circuit unit 105 are connected to each other with the connector 109, a DC power is supplied from the AC adaptor circuit 103 via the AC input receptacle 101 to the charging circuit 104 inside the AC circuit unit 102 and then to the DC circuit unit 105 as an external device.
When the AC circuit unit 102 is connected to the connector 109, the switch SW2 is automatically turned OFF, so that the battery pack 108 is electrically disconnected from other circuits in the DC circuit unit 105. Upon power supply from the AC adaptor circuit 103, the charging circuit 104 starts charging to the battery pack 108.
In this step, when the switch SW1 is turned ON, the AC adaptor circuit 103 and the DC--DC converter 106 are electrically connected to each other, and the DC power outputted from the AC adaptor circuit 103 is supplied also to the DC--DC converter 106. As a result the charging apparatus drives the logic circuit 107 charging the battery pack 108.
After charging is complete, in a case where the AC circuit unit 102 is separated from the connector 109, the switch SW 2 is automatically turned ON, so that each circuit in the DC circuit unit 105 is electrically connected to the battery pack 108. In this case, the DC circuit unit 105 runs using the battery pack 108 as a main power source.
With the charging apparatus based on the conventional technology as described above, after the AC circuit unit 102 comprising the AC adaptor circuit 103 is connected to the DC circuit unit 105 comprising the DC--DC converter 106, an operation for charging the battery pack 108 in the DC circuit unit 105 is started according to the charging control by the charging circuit 104 in the AC circuit unit 102, so that, for the purpose of an application for charging the battery pack 108 with an input power from the AC input receptacle 101, combination of the AC circuit unit 102 and the DC circuit unit 105 is available for the same purpose.
Thus as combination of the AC circuit unit 102 and DC circuit unit 105 is applicable only to the limited applications as described above, it is impossible to use each circuit unit as a single body, and also if a purpose of charging is different, a different charging apparatus must be prepared according to the use, and in that case a number of charging apparatuses according to a number of uses are required.